There are two basic types of underwater lighting installations for swimming pools, spas and the like. One type employs a dry "niche" or housing mounted in the wall of the pool below the water line for the purpose of receiving a lighting fixture. The dry niche is watertight so that pool water is prevented from surrounding the lighting fixture. The other type employs a wet niche, which is also a wall-mounted housing adapted to receive a lighting fixture, but which allows pool water to flow between the niche and the fixture.
Because a dry niche is designed to keep the lighting fixture dry, it must have a watertight seal which inhibits ready access for replacing bulbs, etc. In addition, since the seal must be maintained so as to prevent water from contacting the lighting fixture, it is necessary to service the lighting fixture from the rear of the niche. As can be imagined, these attributes of dry niches complicate manufacture, assembly and maintenance.
Certain disadvantages of dry niches are eliminated with a wet niche. For instance, because the lighting fixture of the wet niche is surrounded by water, there is no need for a watertight frontal seal. As a result, wet niches can be serviced from the front, rather than from the back.
Given the substantial electrical power required for standard lighting fixtures and the increased risk of shock associated with an aqueous environment, wet niches have been made from metal to guarantee adequate grounding (see, for instance, U.S. Pat. No. 4,460,944 and U.S. Pat. No. 3,949,213). In the past, U. L. code regulations have required that: (i) wet niches be made of electric conducting material; (ii) the lighting fixture be grounded through the connecting cord, as well as through the niche; and (iii) each niche be grounded to all other niches in the pool and to a suitable ground, e.g., a water pipe.
While plastic niches are in use in Europe, they are not provided with grounding assurances adequate under U.L. standards. This is due, at least in part, to the fact that the safety regulations imposed in Europe are less stringent than those imposed in the United States pursuant to U.L. code regulations.
Direct current pool lights that run on batteries have also been proposed for use in the United States and Europe. For example, U.S. Pat. No. 4,779,174 discloses a pool light with a plastic housing, the light being powered by direct current generated by flashlight batteries, as opposed to alternating current. Since the light uses such a small amount of power, there is little risk of electric shock associated with water infiltration and therefore grounding assurances are not needed.